[Intel-gfx] [PATCH 45/53] drm/i915/bdw: Do not call intel_runtime_pm_get() in an interrupt

[Chris Wilson]

On Tue, Jul 29, 2014 at 12:26:36PM +0200, Daniel Vetter wrote:
> On Tue, Jul 29, 2014 at 08:37:48AM +0100, Chris Wilson wrote:
> > On Mon, Jul 28, 2014 at 10:54:06AM +0200, Daniel Vetter wrote:
> > > On Sat, Jul 26, 2014 at 11:27:38AM +0100, Chris Wilson wrote:
> > > > On Wed, Jun 18, 2014 at 10:54:13PM +0200, Daniel Vetter wrote:
> > > > > On Fri, Jun 13, 2014 at 04:38:03PM +0100, oscar.mateo at intel.com wrote:
> > > > > > From: Oscar Mateo <oscar.mateo at intel.com>
> > > > > > 
> > > > > > Or with a spinlock grabbed, because it might sleep, which is not
> > > > > > a nice thing to do. Instead, do the runtime_pm get/put together
> > > > > > with the create/destroy request, and handle the forcewake get/put
> > > > > > directly.
> > > > > > 
> > > > > > Signed-off-by: Oscar Mateo <oscar.mateo at intel.com>
> > > > > 
> > > > > Looks like a fixup that should be squashed into relevant earlier patches.
> > > > 
> > > > The whole gen6_gt_force_wake_get() calling intel_runtime_pm_get() is
> > > > broken due to this - we must be able to read registers in atomic
> > > > context!
> > > > 
> > > > Please revert c8c8fb33b37766acf6474784b0d5245dab9a1690
> > > 
> > > force_wake_get can't call runtime_pm_get becuase pm_get can sleep. So if
> > > you want to read registers from atomic context you have to have a runtime
> > > pm reference from someone else.
> > 
> > Nope. That cannot work.
> 
> Well it works currently. So where do you see the problem?

Sampling registers from an timer - in particular, we really do not want
to disable runtime pm whilst trying to monitor the impact of runtime pm.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre